Twenty-one cerebrospinal fluids and corresponding sera have been analyzed for beta-2 microglobulins. This data shows that at least one patient, who had a documented CNS lymphoma, has elevation of the protein in the spinal fluid when compared with the serum. Since the initial patients consist mainly of patients with leukemia, most of whom have had routine lumbar puntures performed to rule out CNS leukemia, it is too early to define the predictive value of beta-2 microglobulin in patients with other malignant diseases. It seems that the protein is not elevated in patients with documented CNS leukemia. 5-Hydroxyindoleacetic acid is currently being evaluated according to the method that we developed. The samples have only been taken through part of the procedure and have been frozen and lyophilized.